Scouting and management of mummy berry in blueberries
It is the time of year again to start looking for germinated mummies under blueberry bushes.
Mummy berry mummies look like tiny black pumpkins (about 3/8 inch in diameter) and may be partially embedded in the soil or located underneath leaf litter. Germinated mummies have small brown finger-like projections (stipes) that eventually develop into apothecia that look like small brown trumpets. There can be anywhere from one to six or seven stipes on a mummy. Depending on soil moisture, only 10 to 20 percent of mummies actually germinate in any one year. During a very wet spring, we have measured up to 40 percent germination, however. In dry fields or dry years, less than 10 percent of the mummies may germinate. It appears that mummies can survive at least two years in fields, but once they have germinated, they die. It is advisable to scout in “hot spots” first, especially wet areas and close to the woods.
In 2010, we set up mummy berry “nurseries” on various Michigan farms. We used metal duct connectors and pushed them three-quarters down into the soil to provide a barrier to keep mummies from being washed or blown away. However, a barrier can be made of any suitable materials, provided that water can flow freely through the soil and the rim is not so high as to cause shading. It may not even be necessary to provide a barrier if the mummies are not at risk of being disturbed. Fifty mummies were collected after harvest when they were still light in color and easy to see and were placed in the enclosure and embedded in the soil surface. Two nurseries were set up per farm in places that are conducive to germination (wetter parts of the field). We will be reporting on their development on a weekly basis until they are spent.
For management of mummy berry, there are various options. First is it important to ascertain that there are mummies in the field and whether they have germinated and that green leaf tissue is present. If you saw shoot strikes or mummified berries in the field last year, it is safe to assume that it is present in the field. If there are infected wild bushes nearby or neighboring fields that have mummy berry, there is also a risk of infection. The wettest sites or areas in the field are at the highest risk. Dormant sprays with lime sulfur appear to suppress the development of functional apothecia, and a ground spray of urea can burn apothecia if they are present. Protective fungicide sprays can prevent primary infections (shoot strikes).
The most effective products are the systemic fungicides Indar (fenbuconazole) and Orbit (propiconazole). These should be applied before or immediately after an infection period (see article Understanding mummy berry shoot strikes by Mark Longstroth). Frost can predispose shoots to infection, and fungicide sprays applied within 24 hours of a frost are advised if the plants are not protected already with an effective fungicide. The protectants Serenade (Bacillus subtilis; add Nu-Film-P adjuvant), Captevate (fenhexamid + captan), Omega (fluazinam), Bravo (chlorothalonil), and Ziram (ziram) can be used as alternate fungicides. In addition, the product Regalia (giant knotweed extract) induces natural resistance in the plant to mummy berry infection and can be used to tank-mix with or in alternation with other fungicides. For prevention of the secondary disease stage (fruit infection), the most effective materials are Indar, Pristine (pyraclostrobin + boscalid), and Omega (fluazinam). Pristine and Omega also provide good control of anthracnose fruit rot and Phomopsis twig blight.